The A flyback converter, also known as a buck-boost converter, is a DC voltage converter, which conveys galvanically decoupled electrical energy between an input and output by means of a transformer. With a flyback converter, a DC voltage supplied to the input can be converted to a DC voltage with another voltage level with little circuitry complexity.
A clocked flyback converter circuit is known from WO 2012/167294 A1, in which a control unit for the primary coil of the transformer controls a grounded switch to be switched on and off for selective clocking of the flyback converter with a specific frequency and switched-on period. The current flowing through the controllable switch is monitored after the switch has been switched off, and the switch is switched back on at a zero crossing of the current. WO 2012/167294 A1 proposes the use of such a clocked flyback converter circuit for a direct power supply to a light emitting diode (LED).
WO 2012/167294 A1 does not disclose, however, how dimming or varying the output power can take place with a direct operation of one or more light emitting diodes on the flyback converter circuit, in particular without a further, actively clocked converter stage.
The light emission of a light emitting diode is a function of the current flow through the light emitting diode. In order to control or regulate the brightness, light emitting diodes are therefore typically operated in a mode in which the current flow through the light emitting diode is modified by an operating device.
WO 2013/092734 A1 discloses a converter for controlling the brightness (dimming) of light emitting diodes by means of pulse width modulation (PWM), in which the duty cycle is modified in a first and second dimming range with a first or second constant amplitude of the LED current, in order to cover a large overall dimming range. The brightness control takes place here only according to a dimmer setting.
For precise control or regulation, in particular with different loads, measurement values must be recorded by the control unit, in order to be able to counteract any potential deviations from predefined operating parameters, such as light color and brightness, or shifting in the light spectrum at different dimming levels.
In order to record the measurement values and generate corresponding signals that can be supplied to and processed by the control circuit, additional components/circuits are needed, making the overall construction complex and expensive.
The invention presents devices and methods that reduce the problems described above. In particular, the object is to create a clocked flyback converter circuit for direct operation of one or more light emitting diodes, and a method for controlling a flyback converter circuit, which allow for a precise control and regulation over a large load range with a simple and inexpensive construction.
This object is achieved in accordance with the features described herein.